Almost all electronic equipment emits various amounts of spurious electromagnetic energy as radio waves and by conduction along power leads and signal leads connected to the equipment. Techniques exist for suppression of the conducted electromagnetic energy but the radiated electromagnetic energy is undesirable as it oftentimes causes interference with the functioning of other equipment which is in close proximity thereto.
Spurious radiated electromagnetic energy also causes another problem. In communications, data processing and other equipment the information being processed can be extracted from the spurious electromagnetic radiation. In government and industrial security applications the signals or data that may be detected may be proprietary or classified in nature and will compromise the security of the system. This is unacceptable in many commercial applications and potentially disasterous in military and other governmental applications in which national security is at stake.
In the past, spurious radiations emanating from equipment have typically been suppressed by completely enclosing the equipment in a shielded container. This is a brute force approach to spurious radiation suppression and there is a need for more acceptable techniques to reduce generation of spurious radiation to acceptable levels.
Accordingly, it is an object of this invention to provide a new and improved keyboard from which spurious radiations are reduced to acceptable low levels.
More particularly, it is an object of our invention to provide an improved keyboard that minimizes generation of spurious radiations rather than suppressing them after generation.